1. Field of the Invention.
This invention relates to an ion exchanger which may be employed in ion chromatography systems for analysis of anions in a sample solution using ion-exchange chromatograph, and to a method of producing the same.
2. Description of the Prior Art.
In ion chromatography systems for analysis of anions in sample solutions using ion exchange chromatographs, there have usually been employed ion exchangers consisting of ion exchange resins as a stationary phase. When an eluent (or mobile phase) is flowing through the ion exchanger, the ion-exchanger resin of a stationary phase exists in a state coupled with opposite ions existing in the eluent. If a sample solution is injected into the ion-exchange chromatograph in such a state, each ion contained in the sample solution undergoes, upon the passing through the ion exchanger, an ion-exchange reaction with the opposite ion coupled with the ion-exchange resin. As a result, each ion is distributed between the eluent (or mobile phase) and the ion exchanger (or stationary phase). Differences in moving rates of ions could develope because the distribution varies with the kind of ions, that is, the affinity for an ion exchanger differs depending on the kinds of ions. Accordingly, ions could be separated in a column packed with an ion exchanger.
It is therefore, no exaggeration to say that an ion exchanger, which has the above described function, determines the capabilities of an ion-exchange chromatography system. A good deal of labor and time have been spent on the study and development of ion exchangers which would optimize efficiency and capacity.
One particular ion exchanger has been disclosed in a published Japanese Patent Application No. 50-77290 dated June 24, 1975, and called "Ion-Exchange Composition".
FIG. 1 herein is a cross sectional view depicting a prior art ion exchanger, such as described in the above Japanese Patent Application. Turning to FIG. 1, a carrier 1 consisting of a styrene-divinylbenzene copolymer, has an outer stratum 2 formed by a technique known as sulphonation. A plurality of fine sized particles 3, made for example by pulverizing an anion-exchange resin are disposed over the carrier 1. Each fine particle 3 has anion-exchange groups, and is electrostatically attached and layered onto outer stratum 2, as depicted.
FIG. 2 is an explanatory diagram showing a method of producing a prior art ion exchanger, such as described in the above Japanese Patent Application. Referring to FIG. 2, the surface of carrier 1 comprised, for example of a styrene-divinylbenzene copolymer is sulphonated by use of a sulfuric acid, and by heating. Next, the surface-sulphonated carrier is packed into a column made of a stainless steel tube.
Concurrently, anion-exchange resin is ground in a mortar, in order to produce fine sized particles thereof. These fine sized particles are suspended in some distilled water, to produce a latex (or suspension). After standing for about one hour, the latex is skimmed. Some skimmed latex is refined by means of a centrifugal separator, and then, a refined latex is injected into the column packed with the carrier. The fine sized particles contained in the latex, are successively attached to the carrier. From the latex detected by analyzing the effluent from the column by use of a spectrophotometer, it is then judged that no more particles can be attached to the carrier. Thus, the ion exchanger illustrated in FIG. 1, for example, is completed as packed in a column.
The above mentioned prior art ion exchanger, has a number of deficiencies, such as that the fine sized anion-exchange particles are liable to become detached from the carrier when it is washed by a concentrated alkaline solution flowing through the column holding the ion exchanger. Also, the separation properties of the fine sized anion-exchange particles are liable to deteriorate when coming into contact with the organic components of sample solutions. Moreover, the method of producing such ion exchangers, such as discussed with reference to the flow diagram of FIG. 2, does not permit ready and easy adjustment of capacity of ion exchange. Thus, the column packed with such prior art ion exchangers, is generally inferior in capability for separating ions.